Generate types for src/service-worker.js

[kwangure]

Describe the problem

At present you need to add types for the service worker to clue TypeScript in about the WebWorker scope and set self to ServiceWorkerGlobalScope.

Describe the proposed solution

SvelteKit should generate types into the types folder.

Alternatives considered

Writing my own types. It typically involves adding triple-slash directives in my src/service-worker.js.

/// <reference no-default-lib="true"/>
/// <reference lib="esnext" />
/// <reference lib="webworker" />

self.addEventListener('install', (event) => {
	/** @type {ExtendableEvent} */ (event).SpecialServiceWorkerStuff

And creating src/service-worker.d.ts

declare const self: ServiceWorkerGlobalScope;

Importance

nice to have

Additional Information

TS Context: microsoft/TypeScript#14877.

[dummdidumm]

We can't generate such types into the types folder because they still need to be manually referenced inside service-worker.js, and at the same time it needs to be made sure that those types are not loaded anywhere else, since the no-default-lib instruction effectively removes theses type definitions from the rest of the project, which is undesireable. I think we should instead document this pattern and adjust our generated tsconfig.json to exclude the service worker file, so it doesn't interfere with the rest of the project.

[jdgamble555]

The problem with this is that if you import anything inside the /src/service-worker folder, it won't find things like $lib etc.